System and method for analyzing acetabular cup position

ABSTRACT

A system and method to identify, convey, and reduce the risk of hip dislocations following hip replacement surgery. Preoperative images are used to identify the pelvic tilt of a patient while the patient is in a sitting position, a standing position, and a supine position. Based on the pelvic tilt and pelvic mobility depicted in the preoperative images, the system can identify a quantitative and/or qualitative risk of hip dislocation when the patient is seated, standing, and lying. During surgery, an intraoperative image can confirm the acetabular cup orientation once implanted and the system can determine the risk of hip dislocation when patient is in the supine position. The system can also extrapolate the dislocation risk when the patient is seated and standing based on acetabular cup position and orientation depicted in the intraoperative image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application is a continuation of InternationalApplication No. PCT/US21/38006 filed on Jun. 18, 2021 and claimspriority to nonprovisional application Ser. No. 17/144,611, entitled“SYSTEM AND METHOD FOR ANALYZING ACETABULAR CUP POSITION,” filed Jan. 8,2021 by the same inventors, which claims priority to (1) provisionalapplication No. 63/043,166, entitled “SYSTEM AND METHOD FOR ANALYZINGACETABULAR CUP POSITION,” filed Jun. 24, 2020 by the same inventors, (2)provisional application No. 63/069,176, entitled “SYSTEM AND METHOD FORANALYZING ACETABULAR CUP POSITION,” filed Aug. 24, 2020 by the sameinventors, and (3) provisional application No. 63/124,272, entitled“SYSTEM AND METHOD FOR ANALYZING ACETABULAR CUP POSITION,” filed Dec.11, 2020 by the same inventors.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates, generally, to acetabular cup implantation. Morespecifically, it relates to a system and method for determining andconveying the risk of hip dislocations for patients undergoing hipreplacement surgery.

2. Brief Description of the Prior Art

Hip replacement surgery requires the implantation of an acetabular cupinto the acetabulum in the pelvis. The acetabular cup houses the femoralhead of the femoral implant in the artificial hip joint. Traditionally,surgeons performing hip replacement surgery position the acetabular cupcomponent during surgery based upon a standard range of acceptablevalues for anteversion and inclination, known as the Lewinnek “SafeZone.” This safe zone is a cup inclination of 40°±10° and a cupanteversion of 15°±10°. Acetabular cups placed within the Lewinnek safezone have traditionally been thought to be relatively safe frompostoperative dislocation. Over the years, many surgeons have determinedthat a more ideal positioning includes the acetabular cup inserted at aninclination angle of roughly 43 degrees and an anteversion angle ofroughly 23 degrees. However, there are many examples of postoperativedislocation in which the acetabular component was positioned within theLewinnek safe zone. This postoperative data identifying dislocationswithin the targeted Lewinnek safe zone has led to an appreciation thathip implant stability is multifactorial and that additional data isneeded to provide a more complete analysis of dislocation risk.

One of the factors understood to affect stability is the realizationthat a patient's effective acetabular anteversion and inclination changeas they move through various positions such as sitting, standing, andsupine. This is due to a change in the patient's pelvic position, knownas “pelvic tilt,” which occurs as a patient changes his/her position.Changes in pelvic tilt directly influence functional anteversion andinclination, which means that acetabular analysis in a single positionpresents an incomplete picture of data and can result in a seriousdislocation risk as it does not account for potential changes due topelvic tilt that occur in various positions.

Notably, the analysis of intraoperative inclination and anteversion datathe is used to guide acetabular component placement is generallyperformed when the patient is positioned in a supine position—preciselythe position in which dislocation risk is the lowest. The surgeon wouldbenefit greatly from understanding how the cup position changes when apatient is in a seated or standing position, which are the functionalpositions that actually present a much higher dislocation risk. Thiswould require a system to incorporate information on how pelvic tiltchanges in these functional positions which would allow for thecalculation of how anteversion and inclination correspondingly change.Providing data on how the acetabular position changes due to changes inpelvic tilt in different functional positions would provide surgeonswith a more complete set of data to use as they assess dislocation risk.

Accordingly, what is needed is a system and method to better identify,analyze, and convey the risk of hip dislocations through a preoperativeanalysis of a patient's pelvis when in multiple anatomical positions.However, in view of the art considered as a whole at the time thepresent invention was made, it was not obvious to those of ordinaryskill in the field of this invention how the shortcomings of the priorart could be overcome.

All referenced publications are incorporated herein by reference intheir entirety. Furthermore, where a definition or use of a term in areference, which is incorporated by reference herein, is inconsistent orcontrary to the definition of that term provided herein, the definitionof that term provided herein applies and the definition of that term inthe reference does not apply.

While certain aspects of conventional technologies have been discussedto facilitate disclosure of the invention, Applicants in no way disclaimthese technical aspects, and it is contemplated that the claimedinvention may encompass one or more of the conventional technicalaspects discussed herein.

The present invention may address one or more of the problems anddeficiencies of the prior art discussed above. However, it iscontemplated that the invention may prove useful in addressing otherproblems and deficiencies in a number of technical areas. Therefore, theclaimed invention should not necessarily be construed as limited toaddressing any of the particular problems or deficiencies discussedherein.

In this specification, where a document, act or item of knowledge isreferred to or discussed, this reference or discussion is not anadmission that the document, act or item of knowledge or any combinationthereof was at the priority date, publicly available, known to thepublic, part of common general knowledge, or otherwise constitutes priorart under the applicable statutory provisions; or is known to berelevant to an attempt to solve any problem with which thisspecification is concerned.

BRIEF SUMMARY OF THE INVENTION

The long-standing but heretofore unfulfilled need for a system andmethod to better identify, analyze, and convey the risk of hipdislocations through a preoperative analysis of a patient's pelvis whenin multiple anatomical positions is now met by a new, useful, andnonobvious invention.

In some embodiments, the present invention includes a method forpreoperatively determining inclination and anteversion for an acetabularcup component of a hip implant in several anatomical positions todetermine a risk of hip dislocation in the several anatomical positions.In some embodiments, the present invention includes a computer systemhaving one or more computers for performing the method.

The method includes acquiring a plurality of preoperative images of apatient's pelvic region. In some embodiments the plurality ofpreoperative images includes an anteroposterior image of the patient'spelvic region in a first anatomical position, a lateral image of thepatient's pelvic region in the first anatomical position, ananteroposterior image of the patient's pelvic region when the patient isin a second anatomical position, and an image of the patient's pelvicregion when the patient is in a third anatomical position. In someembodiments, the image of the patient's pelvic region when the patientis in the third anatomical position is a lateral image. Alternatively,in some embodiments the image of the patient's pelvic region when thepatient is in the third anatomical position is an AP image.

In some embodiments, the first, second, and third anatomical positionsare distinct from each other and each is a seated, standing, or supineposition. In some embodiments, the first anatomical position is thestanding position, the second anatomical position is the supineposition, and the third anatomical position is the seated position.

The present invention further includes determining a sacral femoralpubic angle from the anteroposterior image of the patient's pelvicregion in the first anatomical position; determining a spinal pelvictilt angle from the lateral image of the patient's pelvic region in thefirst anatomical position; and determining a patient specific sacralfemoral pubic constant by adding the sacral femoral pubic angle from theanteroposterior image of the patient's pelvic region in the firstanatomical position to the spinal pelvic tilt angle from the lateralimage of the patient's pelvic region in the first anatomical position.Determining the patient specific sacral femoral pubic constant providesa consistent relationship between an anteroposterior image and a lateralimage when the patient is in the same anatomical position. As such, thepresent invention can use either an AP or a lateral image to preciselydetermine the patient's pelvic tilt in any anatomical position.

The present invention further includes determining a sacral femoralpubic angle from the anteroposterior image of the patient's pelvicregion in the second anatomical position. In addition, the presentinvention determines a spinal pelvic tilt angle of the patient's pelvisin the second anatomical position by subtracting the sacral femoralpubic angle from the anteroposterior image of the patient's pelvicregion in the second anatomical position from the patient specificsacral femoral pubic constant. Finally, the present invention determinesa pelvic tilt angle from the image of the patient's pelvic region whenthe third anatomical position. Once the pelvic tilt data is known foreach anatomical position, the calculated pelvic tilt angles in theseated position, standing position, and supine position allow a surgeonto determine how the inclination and anteversion for the acetabular cupcomponent of the hip implant will vary in each of the seated position,standing position, and supine position.

In some embodiments, the plurality of preoperative images includes alateral image of the patient's pelvic region when the patient is in aseated position, a lateral image of the patient's pelvic region when thepatient is in a standing position, an anteroposterior image of thepatient's pelvic region when the patient is in a standing position, andan anteroposterior image of the patient in a supine position.

The present invention then determines a seated spinal pelvic tilt angleeither directly or indirectly through a sacral slope. Moreover, thepresent invention determines a patient-specific sacral femoral pubicconstant from the preoperative lateral image and anteroposterior imageof the patient's pelvic region when the patient is in the standingposition.

Determining the sacral femoral pubic constant includes determining astanding spinal pelvic tilt angle from the lateral image either directlyor indirectly through the sacral slope; determining a standing sacralfemoral pubic angle from the anteroposterior image; and calculating thesacral femoral pubic constant by adding the standing sacral femoralpubic angle to the standing spinal pelvic tilt angle. Then the presentinvention determines a supine pelvic tilt angle of the patient from thepreoperative image of the anteroposterior view of the patient in thesupine position by subtracting a supine sacral femoral pubic angle fromthe sacral femoral pubic constant.

In some embodiments, directly determining the spinal pelvic tilt anglefor any lateral image includes identifying a vertebral anatomicallandmark; identifying a center point of a femoral head; establishing avertical axis that is vertically aligned with the center point of thefemoral head; and calculating the spinal pelvic tilt angle, whichcorresponds to an angle between the vertical axis and a line extendingfrom the center point of the femoral head to the vertebral anatomicallandmark. In some embodiments, the vertebral anatomical landmark is amidpoint on a line corresponding to a patient's sacral endplate.

In some embodiments, directly determining the spinal pelvic tilt anglefor any lateral image includes digitally registering the vertebralanatomical landmark on the lateral image, digitally registering thecenter point of the femoral head on the lateral image, and digitallyregistering the vertical axis on the lateral image

In some embodiments, indirectly determining the spinal pelvic tilt anglethrough the sacral slope for any lateral image includes identifying avertebral anatomical landmark, establishing a horizontal axis that ishorizontally aligned with a superior point on the line corresponding tothe patient's sacral endplate, determining a sacral slope angle, whichcorresponds to an angle between the horizontal axis and the vertebralanatomical landmark, and calculating the spinal pelvic tilt angle bysubtracting the sacral slope angle from a pelvic incidence of thepatient. In some embodiments, the vertebral anatomical landmark is aline corresponding to the patient's sacral endplate.

In some embodiments, indirectly determining the spinal pelvic tilt anglethrough the sacral slope for any lateral image includes digitallyregistering a vertebral anatomical landmark on the lateral image anddigitally registering a horizontal axis on the lateral image.

In some embodiments, determining a sacral femoral pubic angle from anyanteroposterior image includes identifying a vertebral anatomicallandmark; identifying the center point of the femoral head; identifyinga position of a superior point on a pubic symphysis; establishing afemoral pubic line extending from the center point of the femoral headto the position of the superior point on the pubic symphysis; andcalculating the sacral femoral pubic angle, which corresponds to anangle between the femoral pubic line and a line extending from thecenter point of the femoral head to the vertebral anatomical landmark.

In some embodiments, determining a sacral femoral pubic angle from anyanteroposterior image includes digitally registering a vertebralanatomical landmark on the anteroposterior image, digitally registeringthe center point of the femoral head on the anteroposterior image,digitally registering a position of a superior point on a pubicsymphysis on the anteroposterior image, and digitally registering afemoral pubic line extending from the center point of the femoral headto the position of the superior point on the pubic symphysis on theanteroposterior image.

Once the pelvic tilt values for each anatomical position have beendetermined, the present invention calculates a seated anteversion of theacetabular cup component for the seated position, a standing anteversionof the acetabular cup component for the standing position, a seatedinclination of the acetabular cup component for the seated position, anda standing inclination of the acetabular cup component for the standingposition.

The seated anteversion of the acetabular cup component for the seatedposition is based on:

Anteversion_(Seated)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Seated))*Ant_(Co)

The Anteversion_(Supine) is a predetermined supine anteversion value,SPT_(Supine) is the supine pelvic tilt angle, SPT_(Seated) is the seatedpelvic tilt angle, and Ant_(Co) is an anteversion coefficient.

The standing anteversion of the acetabular cup component for thestanding position is based on:

Anteversion_(Standing)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Standing))*Ant_(Co)

The Anteversion_(Supine) is the predetermined supine anteversion value,SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) is thestanding pelvic tilt angle, and Ant_(Co) is the anteversion coefficient.

The seated inclination of the acetabular cup component for the seatedposition is based on:

Inclination_(Seated)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Seated))*Inc_(Co)

The Inclination_(Supine) is a predetermined supine inclination value,SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) is thestanding pelvic tilt angle, and Inc_(Co) is an inclination coefficient.

The standing inclination of the acetabular cup component for thestanding position is based on:

Inclination_(Standing)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Standing))*Inc_(Co)

The Inclination_(Supine) is the predetermined supine inclination value,SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) is thestanding pelvic tilt angle, and Inc_(Co) is the inclination coefficient.

In some embodiments, the present invention displays to a user thecalculated standing inclination of the acetabular cup component, thecalculated standing anteversion of the acetabular cup component, thecalculated seated inclination of the acetabular cup component, and thecalculated seated anteversion of the acetabular cup component. Someembodiments further include qualitatively conveying if the calculatedstanding inclination of the acetabular cup component, the calculatedstanding anteversion of the acetabular cup component, the calculatedseated inclination of the acetabular cup component, and the calculatedseated anteversion of the acetabular cup component are each in a lowrisk, medium risk, or high-risk zone for hip dislocation.

In some embodiments, the anteversion coefficient is between 0.7 and 0.8.In some embodiments, the inclination coefficient is between 0.2 and 0.4.

In some embodiments, the predetermined supine inclination value isinitially set to 40. In some embodiments, the predetermined supineinclination value is adjustable by a user. In some embodiments, thepredetermined supine anteversion value is initially set to 20. In someembodiments, the predetermined supine anteversion value is adjustable bya user.

Some embodiments further include retrieving an intraoperative imagedepicting an implanted acetabular cup component within a patient's body;determining an intraoperative inclination and an intraoperativeanteversion of the implanted acetabular cup component; and calculatingan intraoperative standing inclination of the acetabular cup componentan intraoperative standing anteversion of the acetabular cup component,an intraoperative seated inclination of the acetabular cup component,and an intraoperative seated anteversion of the acetabular cupcomponent. The depicted implanted acetabular cup component may be thefinal acetabular cup component to be permanently implanted or it may bea guide designed to mimic the final acetabular cup component.

These and other important objects, advantages, and features of theinvention will become clear as this disclosure proceeds.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts that will beexemplified in the disclosure set forth hereinafter and the scope of theinvention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings will be provided by the Office upon request and paymentof the necessary fee.

For a fuller understanding of the invention, reference should be made tothe following detailed description, taken in connection with theaccompanying drawings, in which:

FIG. 1 is a representative diagram illustrating the relationship betweenthe pelvic tilt, sacral slope, and pelvic incidence.

FIG. 2 is an anteroposterior view of a pelvis with the correspondingX-axis, Y-axis, and Z-axis displayed adjacent to the pelvis.

FIG. 3 is a flowchart of an embodiment of the present invention.

FIG. 4 is a system diagram an embodiment of the preoperative module andan embodiment of the intraoperative module.

FIG. 5 is a flowchart capturing an embodiment of the steps ofpreoperative analysis.

FIG. 6 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a circle is drawn around one of the femoral heads.

FIG. 7 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a circle is drawn around the other femoral head.

FIG. 8 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a line is drawn in relation to the sacrum.

FIG. 9 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a first neutral axis line is drawn and the angle betweenthe first neutral axis line and the sacrum line is calculated toidentify the spinal pelvic tilt.

FIG. 10 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a line is drawn from the anterior superior iliac spine(ASIS) to the pubic symphysis.

FIG. 11 is an exemplary preoperative lateral image of a patient's pelvicregion when the patient is in a seated position. The figure depicts thestep in which a second neutral axis line is drawn and the angle betweenthe second neutral axis line and the ASIS line is calculated to identifythe anterior pelvic tilt.

FIG. 12 is an exemplary preoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a line is drawnacross the S1 upper endplate.

FIG. 13 is an exemplary preoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a circle is drawnaround the contralateral femoral head.

FIG. 14 is an exemplary preoperative supine anteroposterior image of apatient's pelvic region depicting the step in which the sacral femoralpubic angle is calculated.

FIG. 15 is an exemplary preoperative standing anteroposterior image of apatient's pelvic region depicting the step in which a line is drawnacross the S1 upper endplate.

FIG. 16 is an exemplary preoperative standing anteroposterior image of apatient's pelvic region depicting the step in which a horizontal axisline is drawn from a posterior point on the S1 upper endplate tocalculate the sacral slope.

FIG. 17 is an exemplary preoperative standing anteroposterior image of apatient's pelvic region depicting the step in which a line is drawnacross the S1 upper endplate.

FIG. 18 is an exemplary preoperative standing anteroposterior image of apatient's pelvic region depicting the step in which a circle is drawnaround the contralateral femoral head.

FIG. 19 is an exemplary preoperative standing anteroposterior image of apatient's pelvic region depicting the step in which the sacral femoralpubic angle is calculated.

FIG. 20A is an embodiment of a graphic display of the hip dislocationrisk in a standing, seated, and lying orientation based on preoperativeanalysis.

FIG. 20B is an embodiment of a graphic display of the hip dislocationrisk in a standing, seated, and lying orientation based on preoperativeanalysis.

FIG. 20C is an embodiment of a graphic display of the hip dislocationrisk in a standing, seated, and lying orientation based on preoperativeanalysis.

FIG. 21 is a flowchart capturing an embodiment of the steps ofpreoperative analysis.

FIG. 22 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a neutral axis isdrawn across the pelvis.

FIG. 23 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a teardrop brim lineis drawn across the pelvis.

FIG. 24 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a line is drawnacross the S1 upper endplate.

FIG. 25 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which a circle is drawnaround the contralateral femoral head.

FIG. 26 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which the SFP angle iscalculated and displayed.

FIG. 27 is an exemplary intraoperative supine anteroposterior image of apatient's pelvic region depicting the step in which the intraoperativeimage of the acetabular cup component is displayed.

FIG. 28 is an embodiment of a graphic display of the hip dislocationrisk in a standing, seated, and lying orientation based on theintraoperative analysis.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings, which form a partthereof, and within which are shown by way of illustration specificembodiments by which the invention may be practiced. It is to beunderstood that other embodiments may be utilized, and structuralchanges may be made without departing from the scope of the invention.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the context clearly dictates otherwise.

The phrases “in some embodiments,” “according to some embodiments,” “inthe embodiments shown,” “in other embodiments,” and the like generallymean the particular feature, structure, or characteristic following thephrase is included in at least one implementation. In addition, suchphrases do not necessarily refer to the same embodiments or differentembodiments.

As used herein, the term “preoperative images” referred to medicalimages showing the patient prior to an intended surgery. While certainembodiments may use any form of medical imaging, radiographic or x-rayimaging, alterative imaging systems may be used to capture theanatomical features of the patient. Some embodiments use 2D medicalimaging. Moreover, the present invention is adapted to receive the imagefiles in any format including, but not limited to .png, .bmp, .jpg, andDICOM format. In some embodiments, the system is configured to accessone or more databases to retrieve the required images.

Intraoperative images are similar to preoperative images except that theintraoperative images are taken while the patient is in operating room(“OR”) or while the surgery is ongoing. Some embodiments use 2Dintraoperative medical imaging.

As used herein, the term “pelvic tilt” refers to the forward or backwardrotation/leaning of the pelvis. An example of pelvic tilt is depicted inFIG. 1 .

As used herein, “sacral slope” refers to the angle between thehorizontal axis and the sacral endplate. In some embodiments, the sacralslope can be determined by relying on other vertebral anatomicallandmark, however, different vertebral anatomical landmark will alterthe constants and the pelvic incidence. To ensure accuracy, the samevertebral anatomical landmark should be used throughout the preoperativeand intraoperative analyses.

As used herein, the “sacral-femoral-pubic angle” (“SFP angle”) iscalculated between a line extending from a midpoint of the vertebralanatomical landmark to the center of a femoral head, and a lineextending from the superior point of the pubic symphysis to the centerof a femoral head, as shown in an anteroposterior view. In someembodiments, “sacral-femoral-pubic angle” (“SFP angle”) is calculatedbetween a line extending from a midpoint of the sacral endplate to thecenter of a femoral head, and a line extending from the superior pointof the pubic symphysis to the center of a femoral head, as shown in ananteroposterior view.

As used herein, the “spinopelvic tilt angle” (“SPT angle”) is areference of the amount of forward or backward learn of the pelvic, asshown in a lateral image. The SPT angle can be calculated as the anglebetween a line running from the vertebral anatomical landmark midpointto the center of the femoral head and the vertical axis. In someembodiments, the SPT angle is calculated as the angle between a linerunning from the sacral endplate midpoint to the center of the femoralhead and the vertical axis.

As used herein, “pelvic incidence” refers to the angle between a lineperpendicular to the sacral plate at its midpoint and a line connectingthis point to the femoral head axis. Pelvic incidence establishes arelationship between the pelvic tilt and the sacral slope. The tilt andthe slope are inversely reciprocal. More specifically, the pelvicincidence angle equals the sum of the sacral slope angle and the SPTangle. Thus, if you know the pelvic incidence of any view (always thesame) and you know either the sacral slope or SPT angle. As a result,the pelvic incidence can be used to determine the missing value ofeither the sacral slope or SPT angle.

As used herein, the term “supine” refers to a position in which thepatient is lying in a generally flat orientation. Typically, the patientis lying on his/her back when capturing images for a hip replacementsurgery.

It is also important to understand the different terminologycorresponding to the various views and axes that will be discussedherein. An anteroposterior (AP) view or image is one in which an imageis taken from a front side of the patient. It should be noted that an APimage could be replaced by a posteroanterior image, however, it is muchmore common to image a patient from an AP perspective. For ease ofdescription and clarity, the detailed description section and exemplaryfigures will focus on the use of AP images.

The term “AP supine image” refers to an image taken from a front side ofthe patient while the patient is in a supine or lying position. Whilethe AP image could also be a posteroanterior image, it is much morecommon to image a supine patient from an AP perspective. For ease ofdescription and clarity, the embodiment of the present inventiondescribed in relation to exemplary figures will use AP supine images.

Likewise, the term “AP standing image” refers to an image taken from afront side of the patient while the patient is in a standing position.Again, the AP image could also be a posteroanterior image, however, itis much more common to image a patient from an AP perspective.

As used herein, the term “lateral image” refers to an image taken from alateral side of the patient. A person of ordinary skill in the art willunderstand that a perfectly lateral view can be difficult to capture andthat minor angular offsets from a perfectly lateral image are stilluseable with the present invention as will be explained in greaterdetail below.

Accordingly, the term “lateral seated image” refers to an image takenfrom a lateral side of the patient while the patient is in a seatedposition. The term “lateral relaxed seated image” refers to an imagetaken from a lateral side of the patient while the patient is in arelaxed seated position. Some embodiments use a preoperative lateralimage when the patient is in a flexed seated position rather than arelaxed seated position. For ease of description and clarity, theembodiment of the present invention described in relation to exemplaryfigures only includes lateral relaxed seated images.

Finally, the term “lateral standing image” refers to an image taken froma lateral side of the patient while the patient is in a standingposition.

It is also important to understand the terminology involving theorientation of the acetabular cup. When viewing a pelvis from an APview, the inclination angle (aka the “abduction angle”) of the cup isthe degree of rotation about the X-axis (extends laterally across thepelvis). In other words, the inclination angle represents theinclination of the acetabular component within the coronal plane.

From an AP view, the anteversion angle is the degree of rotation of thecup about the Z-axis (extends perpendicular to the plane in which thepelvis resides when viewed from an AP view). In other words, anteversionis a measure of acetabular inclination within the sagittal plane. TheX-, Y-, and Z-axes of a pelvis from an AP view are shown in FIG. 2 .

Referring now to the specifics of the present invention, someembodiments, include a system having a memory, a user interface with avisual display, and a processor for executing a program performing atleast the steps described herein. In some embodiments, the presentinvention is a computer executable method or is a method embodied insoftware for executing the steps described herein. Further explanationof the hardware and software can be found in the Hardware and softwareinfrastructure examples section below.

The present invention includes a system and/or method to identify,convey, and reduce the risk of hip dislocations following hipreplacement surgery. To do so, the present invention uses preoperativeimages of the patient when in at least the following anatomicalpositions: seated, standing, and lying (i.e., supine). The collection ofpreoperative images is used by a preoperative module to identify thepelvic orientation while a patient is in each of the seated, standing,and supine positions. The present invention is configured to use thisinformation to determine an ideal range for the anteversion andinclination angle of the acetabular cup component of a hip implant toreduce the risk of dislocation in each of the anatomical positions. Someembodiments further include an intraoperative module that usesintraoperative image(s) to determine the intraoperative anteversion andinclination angle of the acetabular cup component of a hip implant toidentify the risk of dislocations in each of the seated, standing, andsupine positions.

FIG. 3 provides a broad overview of the workflow of an embodiment ofpresent invention generally denoted by reference numeral 10. The systemor method is initiated at step 12 and a preoperative module performs aseries of procedures at step 14. At step 16 the system displays thepreoperative pelvic tilt data and target range for the anteversion andinclination angle of the acetabular cup component of a hip implant basedon a preoperative analysis of the patient's anatomy. Some embodiments ofthe present invention also initiate an intraoperative module at step 18.The intraoperative module determines the anteversion and inclinationangle of an implanted acetabular cup and analyzes the risk of hipdislocation in each of the seated, standing, and supine positions. Thesystem then displays the results on a user interface at step 20. Uponsatisfactory results, a user can end the program at step 22.

FIG. 4 provides a general overview of the architecture of an embodimentthe system of the present invention. Preoperative module 200 includesimage acquisition module 202, image annotation module 204, calculationengine 206, pelvic position analysis module 208, and pelvic positionoutput module 210. Intraoperative module 300 includes image acquisitionmodule 302, image annotation module 304, calculation engine 306,acetabular component analysis module 308, and acetabular componentposition output module 310. The operational details of the variousmodules will be explained in greater detail below.

Preoperative Module

As will be explained in greater detail herein, the preoperative moduleand its corresponding workflow provide a unique ability to identify apatient specific SFP constant. The SFP constant provides the correlationbetween a patient's SPT angle, as shown in a lateral image, and apatient's SFP angle, as shown in an AP image. The correlation betweenthe set of images (an AP image and a lateral image) remains constantregardless of whether the set of images capture the patient in a seated,standing, or supine position. This correlation is provided in Equation 1below:

SPT_(angle)=SFP_(constant)−SFP_(angle)  (Eq. 1)

Past research has established that the value of the SFP constant shouldbe 75 degrees. However, an SFP constant of 75 only applies to a subsetof the population and reliance on this value could ultimately have adrastic impact on the hip dislocation risk corresponding to a hipreplacement surgery. Thus, some embodiments of the preoperative moduleare configured to determine a patient-specific SFP constant therebyallowing a surgeon to determine a patient's pelvic tilt from an AP imageas needed.

Accordingly, some embodiments of the present invention include a step ofanalyzing (1) a preoperative AP image when the patient is in a firstanatomical position and (2) a preoperative lateral image in the sameanatomical position to calculate a patient specific SFP constant, whichimproves the precision of the analysis. This set of two images—an APimage and a lateral image—can be gathered in any anatomical position.This disclosure describes the set of images as a lateral standing imageand an AP standing image because a standing position is the easiestposition to clearly capture both a lateral and an AP image. However,some embodiments could use a set of lateral and AP supine images or aset of lateral and AP seated images to determine the patient specificSFP constant.

Referring now to FIG. 5 , an embodiment of preoperative module 200performs the steps shown in flowchart 400. Preoperative module 200 isinitiated at step 402 performs the following steps with or without userinput. In some embodiments, preoperative module 200 guides the userthrough a predetermined workflow that begins with thereceipt/acquisition of preoperative radiographic images. It should benoted that the order of image acquisition for the various anatomicalpositions and order of analyzing said images as shown in FIG. 5 can berearranged without departing from the invention.

Preoperative module 200 acquires at least a seated, standing, and supinepreoperative image. In some embodiments, preoperative module 200acquires a lateral seated image, an AP supine image, a lateral standingimage and/or an AP standing image. In some embodiments, the lateralseated image is a lateral relaxed seated image, which is sometimespreferable when establishing spinal tilt.

In addition, as previously noted the set of lateral and AP images may beseated or supine images rather than standing images. Similarly, theseated image may be an AP image and the supine image may be a lateralimage. In some embodiments, the preoperative images of the patient inthe standing, seated, and supine orientations are captured from eitherthe AP or lateral views. In some embodiments, the preoperative images ofthe patient in the standing, seated, and supine orientations arecaptured from both the AP and lateral views. However, for the sake ofbrevity and clarity, this section will focus on the use of a lateralseated image, an AP supine image, a lateral standing image and an APstanding image.

In addition, some embodiments include an image orientation step tomodify one or more images to better capture the patient's pelvicposition/orientation as it exists in reality. Alternatively, the imagecapturing device is first properly oriented prior to capturing the imageto ensure that the image depicts the pelvis in the sameposition/orientation as it exists in reality. In some embodiments, theuser is provided with the option to manually rotate the preoperativeimage as needed to better capture the true orientation of a patient'spelvis in reality.

As previously explained, the preoperative images are used to identifythe pelvic tilt and how the pelvic tilt changes in each of the seated,standing, and lying positions, which is used to determine an ideal rangefor the anteversion and inclination angle of the acetabular cupcomponent of a hip implant. Thus, preoperative module 200 is configuredto determine the pelvic tilt in the various anatomical positions fromthe preoperative images.

In some embodiments, the pelvic tilt is determined directly by measuringthe spinal pelvic tilt (SPT) angle from a lateral view. In someembodiments, the pelvic tilt is measured indirectly through the angle ofthe sacral slope from a lateral view by relying on the pelvic incidence.Some embodiments determine the pelvic tilt indirectly by measuringsacral femoral pubic (SFP) angle as seen in an AP view. The differentapproaches will be discussed in connection with certain images andcertain anatomical positions; however, it should be noted that thepelvic tilt for any of the anatomical positions (seated, standing, andsupine) can be determined from either (1) lateral images using the SPTangle and/or the sacral slope or (2) AP images using the SFP angle.

Regardless of how the pelvic tilt angle is determined, the presentinvention uses anatomical landmarks to determine the relevant angles andpelvic tilt. The anatomical landmark may be points, lines, circles, orother types of digitally registerable annotations corresponding to oneor more aspects of the patient's anatomy. In some embodiments, theanatomical landmarks are determined manually by a user whereas someembodiments image annotation module 204 automatically identifies theanatomical landmarks through image recognition software or machinelearning algorithms. Some embodiments employ a mix of automated andmanual identification of the anatomical landmarks. Moreover, someembodiments, allow the user to modify the location of the visuallydisplayed anatomical landmarks points to account for imaging or locationerrors.

In some embodiments, some or all of the anatomical landmarks aredigitally inserted or overlaid onto the images to provide a visualindication of the location of the anatomical landmarks. While differentmethods of visually displaying the landmarks may be used, the term“digitally register” will be used herein to refer to any method used tovisually depict an anatomical landmark on a digital image. In someembodiments, preoperative module 200 visually displays to a user eachinstance in which an anatomical landmark is digitally registered on oneof the preoperative images similar to FIGS. 6-19 .

Some embodiments may perform the steps of determining the SPT angle,sacral slope, and/or SFP angle without visually displaying theanatomical landmarks or other visual indicia. Some embodiments mayvisually display only a subset of the anatomical landmarks or othervisual indicia. However, the detailed description section and theexemplary images will focus on embodiments in which each step isvisually displayed to better convey the steps of the present invention.

Determining Pelvic Tilt in the Various Anatomical Positions

Referring now to FIGS. 4 and 5 in combination, an embodiment ofpreoperative module 200 includes image acquisition module 202 acquiringa plurality of preoperative images at steps 404, 418, 426, and 432. Aspreviously noted, the order of image acquisition for the variousanatomical positions and order of analyzing said images as shown in FIG.5 can be rearranged without departing from the invention. For example,some embodiments perform steps 426-440 in order to determine a patientspecific SFP constant prior to determining the pelvic tilt from an APimage such as in step 424.

In addition, the method of determining the pelvic tilt in eachanatomical position can vary depending on whether the image is an APimage or lateral image. Moreover, the method for determining the pelvictilt from a lateral image can vary depending on the ease of whichcertain anatomical features can be identified. These various methodswill be described in more detail below in relation to the exemplaryflowcharts of FIGS. 4 and 5 and the exemplary images of FIGS. 6-19 . Forthe sake of brevity and clarity determining pelvic tilt in a lateralimage by relying on the femoral head(s) is described in relation to anacquired lateral seated preoperative image in steps 406-412 in FIG. 5 ;determining pelvic tilt in a lateral image by relying on the sacralslope is described in relation to an acquired lateral standingpreoperative image in steps 428-430 in FIG. 5 ; and determining thepelvic tilt from an AP image is described in steps 420-424 of FIG. 5 inrelation to the preoperative supine AP image. However, the method ofdetermining the pelvic tilt in each anatomical position can varydepending on whether the image is an AP image or lateral image.

Seated Pelvic Tilt

Referring back to FIGS. 4 and 5 in combination, an embodiment ofpreoperative module 200 includes image acquisition module 202 acquiringa lateral seated preoperative image at step 404. Image annotation module204 then performs steps 406 through 410, which are exemplified in FIGS.6-9 , in order to directly determine the SPT angle. As previously noted,some embodiments alternatively calculate the sacral slope in the seatedlateral image and some embodiments calculate the SPT angle through theSFP angle shown in a seated AP image.

As explained in step 406 in FIG. 5 and illustrated in FIG. 6 , thepresent invention directly calculates the SPT angle from the lateralimage, by first digitally registering an anatomical landmark in the formof circle 102 around femoral head 104 in the preoperative image. Theanatomical landmark can be manually or automatically digitallyregistered. In some embodiments, the center point of the femoral head isdetermined and/or digitally registered on the preoperative image ratherthan using a circle. Similarly, an embodiment may identify the centerpoint of the acetabulum rather than relying on location of the femoralhead.

In some embodiments, the lateral image is not an exact lateral image andas a result, the patient's femoral heads are not laterally aligned. Insuch an instance, as explained in step 408 in FIG. 5 and illustrated inFIG. 7 , the center of the patient's other lateral head 106 oracetabulum is identified by an anatomical landmark, such as the centerpoint or circle 108 depicted in FIG. 7 . The midpoint between the centerpoints of each femoral head becomes the vertex of the spinal tilt angle(see FIG. 9 ).

The system then automatically or instructs a user to manually digitallyregister an anatomical landmark in relation to the sacrum at step 410.As shown in FIG. 8 , the depicted anatomical landmark is line segment110 outlining superior endplate 112 of the S1 vertebrae from theanterior to posterior border (i.e., from end to end). With theanatomical landmarks identified, calculation engine 206 can calculatethe SPT angle at step 412. As previously noted, different vertebrae anddifferent structural features of vertebrae may be used as the anatomicallandmark, so long as appropriate correction factors are used. Regardlessof which vertebral anatomical landmark is used, it should remain thesame for the analyses of the other images to maintain precision.

In order to calculate the SPT angle in step 412, midpoint 114 of linesegment 110 is identified and used as one of the endpoints fordetermining the SPT angle. In some embodiments, the midpoint of thesacral plate is visually determined without first outlining the sacrumwith a line segment.

Line 116 extending from vertex 118 between the femoral heads to midpoint114 of the sacrum line establishes a first vector defining the SPTangle. The system then digitally registers first neutral axis 120extending vertically from vertex 118, which is the second vectordefining the SPT angle. Calculation engine 206 can then use the twovectors to calculate the SPT angle.

Once the SPT angle is calculated, pelvic position display module 208 canthen display the angle between the first and second vectors as depictedin FIG. 9 to visually convey the SPT angle when the patient is in theseated position. Alternatively, the system can forego the digitalregistration of one or both vectors and simply calculate the SPT anglebetween the two.

It should be noted that the first neutral axis is parallel to what wouldbe a line normal to the Earth's surface, i.e., a line parallel to thedirection of the force of gravity. In some embodiments, the preoperativeimages are first oriented/reoriented to ensure that the vertical neutralaxis will align with a line normal to the Earth's surface.Alternatively, the imaging capturing system is initially oriented toensure that the captured images will show the patient's anatomy in theintended orientation such that the vertical neutral axis will align witha line normal to the Earth's surface. In some embodiments, the user isprovided with the option to manually rotate the preoperative image asneeded to better capture the true orientation of a patient's pelvis inreal time.

In some embodiments, the system further determines the sacral slope ofthe patient while in the seated position. Since determination of the SPTangle already requires a step of outlining the S1 endplate, the systemcould use this same anatomical landmark to easily calculate the sacralslope. To do so, image annotation module 204 digitally registers ahorizontal line from the higher endpoint of the S1 endplate landmark.Calculation engine 206 can then calculate sacral slope—the angle betweenthe line outlining the S1 endplate and the horizontal line. In someembodiments, the system displays the sacral slope angle to the user. Insome embodiments, the sacral slope is calculated but not displayed.Ultimately, the angle of the sacral slope plus the SPT angle providesthe pelvic incidence, which is consistent in every anatomical position.

In some embodiments, the sacral slope is based on the endplate of the S1vertebrae. However, the alternative vertebrae can be used, including butnot limited to other sacral vertebrae and lumbar vertebrae. In addition,structural features of the vertebrae may be relied upon instead of theendplates. As previously explained, regardless of which vertebralanatomical landmark is used, it should remain the same for the analysesof the other images to maintain precision.

In some embodiments, the pelvic tilt from lateral images is alwaysdetermined using the sacral slope. The sacral slope does not rely on thefemoral heads which can be difficult to accurately identify in medicalimaging. In addition, the sacral slope changes at a 1:1 rate with theSPT angle based on pelvic incidence. Thus, measuring the sacral slope isan alternative and easier approach to determine pelvic tilt.

In some embodiments, the system further determines an anterior pelvictilt (APT) angle to provide greater clarity in the display of thepatient's pelvis in the implant analysis interface depicted in FIG. 20 .To determine the APT angle, the system automatically, or instructs auser to manually perform the following steps. First, as explained instep 414 in FIG. 5 and illustrated in FIG. 10 , image annotation module204 digitally registers line 122 from the anterior superior iliac spine(ASIS) to the superior point on the pubic symphysis (see FIG. 5 ). Thenat step 416 second neutral axis 124 is digitally registered verticallyfrom the superior point on the pubic symphysis (see FIG. 11 ).Calculation engine 206 determines the APT angle between second neutralaxis 124 and the line 122 extending between the ASIS and the superiorpoint on the pubic symphysis. Similar to the determination of the SPTangle, the system can forego the digital registration of one or bothlines and simply calculate the APT angle between the two. In someembodiments, pelvic position display module 208 displays the APT angleto the user on the user interface as exemplified in FIG. 11 .

The sign (+ or −) of the APT angle is dependent on whether the ASIS iscloser or further to the sacrum (or center of femoral heads) than thepubic symphysis. If ASIS is closer the angle is negative, if ASIS isfurther the angle is positive. In addition, the preoperative image canbe either left or right for either body side. A check needs to beperformed prior to calculating the angle. If the pubic symphysis ‘X’value is less than the femoral head center the image is left at theforefront. If the pubic symphysis ‘X’ value is greater than the femoralhead center the image is right at the forefront.

Supine Pelvic Tilt

As previously explained, in the vast majority of instances, an AP imageis captured when the patient is in a supine position. Thus, while alateral image can be used in accordance with the steps above or inaccordance with the steps corresponding to the determination of a sacralslope (described in the standing pelvic tilt section), this section willfocus on the steps for determining the SPT angle while the patient is ina supine position using an AP image. The steps are described in theflowchart of FIG. 5 and illustrated in FIGS. 12-14 .

As shown in FIG. 5 , image acquisition module 202 acquires apreoperative supine AP image at step 418. Image annotation module 204then digitally registers line 126 across the upper endplate of the S1vertebrae (see FIG. 12 ) at step 420. At step 422, image annotationmodule 204 digitally registers center point 128 of the contralateralfemoral head using circle 130, which is illustrated in FIG. 13 . Centerpoint 128 of the femoral head is identified as the vertex of the SFPangle. First line 132 extends between vertex 128 and midpoint 134 of theS1 vertebrae line 126 and second line 136 extends between vertex 128 andsuperior point 138 on pubic symphysis. The angle between the two lines132 and 136 is the SFP angle. Calculation engine 206 determines the SFPangle at step 424 and pelvic position display module 208 displays theangle as shown in FIG. 14 . Having determined the SFP angle, the systemthen calculates the SPT angle based on Equation 1:

SPT_(angle)−SFP_(constant)−SFP_(angle)  (Eq. 1)

For most patients, the SFP constant is set to 75, however, as previouslyexplained a patient specific SFP constant can be determined by comparingthe preoperative AP standing image and the preoperative lateral standingimage, which will be described in the Standing pelvic tilt sectionbelow. Furthermore, an embodiment of the present invention can rely ondifferent vertebrae for the anatomical landmark in step 420, includingbut not limited to any of the sacral and lumbar vertebrae. However, theuse of different vertebrae will result in different SFP constants andthe vertebral anatomical landmark point should remain constant with theanalyses of the other images.

In some embodiments, the step of identifying or digitally registeringthe vertex of the SFP angle includes identifying (manually through anend user or automatically using software) the non-operative femoralhead. Often the operative femoral head requires operation because itslocation or anatomical structure has been compromised. Reliance on theoperative head would therefore likely result in a vertex location (andthus an SFP angle) that is not a true representation of the patient'soriginal uncompromised anatomy. For that reason, the vertex isidentified in relation to the non-operative femoral head, which in mostcases will provide a more accurate representation of the patient's trueoriginal anatomy and produce better outcomes. Thus, some embodimentsinclude a user-input step in which the user identifies which hip is theoperative hip and/or which hip is the non-operative hip.

In some embodiments, the position of superior point on pubic symphysisis estimated based on the ‘Y’ coordinate of center of femoral headcircle, and ‘X’ coordinate of the midpoint of the vertebrae line. Inaddition, digitally registering the superior point on the pubicsymphysis, like other anatomical landmarks, may be accomplished throughimage recognition software or through user input.

As mentioned above, the present invention may determine the patient'spelvic tilt while the patient is in a supine position using a lateralimage of the pelvis. This can be accomplished by calculating the SPTangle as describe in the Seated pelvic tilt section and/or the pelvictilt can be determined based on the sacral slope as will be described inthe Standing pelvic tilt section.

Standing Pelvic Tilt

To reiterate, this section describes the steps for determining thepelvic tilt from a lateral image using the sacral slope. The sacralslope does not rely on the femoral heads which can be difficult toaccurately identify in medical imaging. In addition, the sacral slopechanges at a 1:1 rate with the SPT angle based on pelvic incidence.Thus, measuring the sacral slope is an alternative and easier approachto determine pelvic tilt if the pelvic incidence is known. However, thepelvic tilt could be determined based on calculating the SPT angle asdescribed in the Seated pelvic tilt section.

This section also describes an embodiment including steps for (1)determining the pelvic tilt of a patient when in a standing positionusing the sacral slope as determined from a lateral image and (2)determining the SFP angle as determined from an AP image when thepatient is in a standing position, and (3) calculating the patientspecific SFP constant. However, some embodiments only use a lateral oronly an AP image to determine the pelvic tilt of the patient when in astanding position.

Referring now to FIGS. 5 and 15-16 , image acquisition module 202acquires a preoperative lateral standing image at step 426. Imageannotation module 204 digitally registers line 140 from the anterior toposterior border of the S1 endplate at step 428, which is illustrated inFIG. 15 . Image annotation module 204 can then digitally registershorizontal line 142 from the higher endpoint of the S1 endplate landmark140. Calculation engine 206 calculates the angle between line 140outlining the sacral endplate and horizontal line 142 and pelvicposition display module 208 displays the sacral slope at step 430. Thedisplay of the sacral slope angle is illustrated in FIG. 16 .

While the described embodiment determines the sacral slope using theendplate of the S1 vertebrae, alternative vertebrae can be used,including but not limited to other sacral vertebrae and lumbarvertebrae. In addition, structural features of the vertebrae may berelied upon instead of the endplates. However, the vertebral anatomicallandmarks should coincide with those used in the analyses of the otherimages.

Some embodiments further include steps for determining the SFP anglefrom an AP view when the patient is in a standing position. The reasonfor using a lateral image and an AP image is to calculate a patientspecific SFP constant rather than relying on the less precise value of75. The value of the SFP constant of the patient remains constantregardless of the patient's anatomical position and is valuable inproducing more accurate data when the intraoperative image is an APimage.

The steps for determining the SFP angle while the patient is in astanding position using an AP image are the same as those described in420-424 in FIG. 5 . Referring to FIGS. 5 and 17-19 , image acquisitionmodule 202 acquires a preoperative AP image of a patient's pelvic regionwhen the patient is in a standing position at step 432. Image annotationmodule 204 then digitally registers line 142 across the upper endplateof the S1 vertebrae (see FIG. 17 ) at step 434. At step 436, imageannotation module 204 digitally registers center point 144 using circle146 around the contralateral femoral head, which is illustrated in FIG.18 . Center point 144 of the femoral head is identified as the vertex ofthe SFP angle. First line 148 extends between vertex 144 and midpoint150 of the S1 vertebrae line and second line 152 extends between vertex144 and superior point 154 on the pubic symphysis. The angle between thetwo lines is the SFP angle. Calculation engine 206 determines the SFPangle at step 438 and pelvic position display module 208 displays theangle as shown in FIG. 19 .

Having determined the SFP angle form the AP image, and knowing the SPTangle from the lateral image, the system then calculates SFP constantusing Equation 1. Some embodiments use the patient specific SFP constantto more precisely calculate the pelvic tilt of the patient from thesupine AP image.

Again, the vertebral anatomical landmark can be any of the sacral andlumbar vertebrae. However, the use of a different vertebrae will resultin a different SFP constant. Thus, the same vertebral anatomicallandmark must be used in each of the steps to ensure that the SFPconstant remains accurate.

While the specification describes an embodiment in which an AP andlateral image are captured while the patient is in the standing positionto calculate a patient specific SFP constant, other embodiments can usethe seated or supine positions to capture both lateral and AP images tocalculate the patient specific SFP constant.

Preoperative Analysis

The preoperative analysis is important because different parameters indifferent functional positions may present different dislocation risks.For example, consider that a standing patient will generally dislocateto the anterior, and therefore more anteversion in a standing positionpresents additional risk. The flex seated position on the other handpresents more risk of a posterior dislocation. Therefore, it isimportant to see how the risk in each position changes with theorientation/position of the acetabular cup component.

Generally, for the seated position, the safe zone is an anteversionvalue above 19 degrees, a medium risk zone is an anteversion valuebetween 10 and 19 degrees, and a high-risk zone is an anteversion valueless than 10 degrees. For the standing position, the safe zone is ananteversion value between 10 and 25 degrees, the medium risk zone is ananteversion value between 25 and 35 degrees, and the high-risk zone isan anteversion value less than 10 degrees and greater than 35 degrees.The system uses these values to assess the dislocation risk in thepreoperative analysis. In some embodiments, the values that define therisk zones can be adjusted by a user.

Following the determinations of the patient's pelvic tilt data in theseated, supine, and standing positions, the system displays the pelvicposition analysis data to an end user (typically the orthopedic surgeon)at step 440 to allow the user to determine the preferred orientation ofthe acetabular cup component of the implant. An example of how thepreoperative pelvic position analysis data can be conveyed is found inFIG. 20 . As shown in FIG. 20A, an embodiment of display 500 includesthe data associated with pelvic tilt for each anatomical position in aseries of boxes on the left-hand side of the screen, which is generallyidentified by reference numeral 508.

Display 500 also preferably displays one or more 3-dimensional images ofthe patient's pelvis, or a representative pelvis, with a digitalrepresentation of an acetabular cup component residing in the acetabulumin display window 502. Preferably, display 500 allows a user to see thepelvis in each anatomical position: seated, standing, and lying. Thiscan be done in a video type format as depicted in FIG. 20A or in aside-by-side manner as shown in FIGS. 20B-20C.

Moreover, the end user is provided with the ability to adjust thelocation and orientation of the acetabular cup in each representativeimage using graphic interfaces 504 (depicted as “+” and “−” buttons) toalter the anteversion and inclination data of the acetabular cupcomponent. The inclination and anteversion can be adjusted in both thepositive and negative directions.

The supine position is the preferred modifiable position because this isthe position in which the patient resides during surgery. Thus, thesurgeon will have a clear understanding of how the surgeon'smodification of the acetabular cup component during surgery will impactthe patient's dislocation risk after the surgery is complete andespecially when the patient is in the higher risk positions—sitting andstanding.

In some embodiments, the supine anteversion and inclination values areset to default values. Preferably the default resides within theLewinnek safe zone. The exemplary depicted embodiment uses a defaultanteversion of 20 degrees and a default inclination angle of 40 degrees.In some embodiments, the predetermined supine anteversion value isinitially set to a value between 20 and 30 degrees.

Based on the patient's pelvic tilt and the inclination and anteversionangles of the representative cup, the system calculates and displays thedislocation risk of the prosthetic hip when the patient is seated,standing, and lying. The risk can be displayed in summary box 506 and/orprovided in a graphic representation, such as tilt bars 510.

In some embodiments, the risk summary box 506 is based upon theconfigured range parameters for the minimum and maximum anteversion andspinal mobility. If the relaxed seated anteversion is less than a knownminimum safe anteversion (configurable) and the standing anteversion isgreater than a known maximum safe anteversion (configurable), then thesystem displays “Risk Assessment: Anterior and Posterior DislocationRisk.” If relaxed seated anteversion is less than a known minimum safeanteversion then the system displays “Risk Assessment: PosteriorDislocation Risk.” If seated anteversion is greater than the knownmaximum safe anteversion then the system displays “Risk Assessment:Anterior Dislocation Risk.” Otherwise, the system displays “NormalDislocation Risk”

If the preoperative sacral slope in the seated position minus thepreoperative sacral slope in the standing position is less than spinalmobility threshold value (configurable) then the system displays “SpinalMobility: Decreased Spinal Mobility.” Otherwise, the system displays“Spinal Mobility: Normal Spine Mobility.”

In some embodiments, tilt bars 510 are correspond to the anteversionvalue of the acetabular cup component. In an embodiment, tilt bars 510will have a red section to indicate zones of high risk, a yellow sectionto indicates zones of medium risk, and a green section to indicate asafe zone. Thus, a cup position having an anteversion value that fallsin the high risk/red section is in danger of dislocation. Thedislocation risk is less in the medium risk/yellow section, but stillconcerning, and finally, the safest/green section is the ideal section.

Preferably display 500 includes both a quantitative measurement of theanteversion and inclination values for the various anatomic locations.Some embodiments also include qualitative indicators (colors to identifya safe zone, a medium dislocation risk zone, and a high dislocation riskzone) to convey the risk of dislocation when the patient is in variousanatomical positions.

In order to properly convey how modification of the inclination andanteversion of the acetabular cup component in one of the anatomicalpositions alters the dislocation risk to the patient in other anatomicalpositions, the system employs the following equations:

Anteversion_(Sitting)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Sitting))*Ant_(Co)  (Eq.2)

Inclination_(Sitting)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Sitting))*Inc_(Co)  (Eq.3)

Anteversion_(Standing)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Standing))*Ant_(Co)  (Eq.4)

Inclination_(Standing)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Standing))*Inc_(Co)  (Eq.5)

Where Ant_(Co) is an anteversion coefficient and Inc_(Co) is aninclination coefficient. In some embodiments, the anteversioncoefficient is 0.75. In some embodiments the anteversion coefficient isa value within the range of 0.7-0.8. In some embodiments it is a valuewithin the range of 0.6-1. In some embodiments, the inclinationcoefficient is 0.29. In some embodiments, the inclination coefficient isa value within the range of 0.2-0.4.

Each time the user modifies the supine anteversion and inclinationvalues, the system automatically inputs the values into Equations 2-5 todetermine the standing and sitting anteversion and inclination values ofthe acetabular cup component. The embodiments in which the standinganteversion and inclination and/or the sittings anteversion andinclination values are adjustable includes the system automaticallycalculating the non-adjusted anteversion and inclination values inaccordance with algebraically reorganized expressions of Equations 2-5.

In some embodiments, the system provides the user with view modificationelements to allow the surgeon to manipulate the orientation of thepelvis and in turn the acetabular cup component. View modificationelements include but are not limited to an AP view toggle, a lateralview toggle, and a slider style control that rotates the pelvis aboutits Z-axis. Alternative controls may be provider to enable a user tomodify the view of the pelvis/acetabular cup component.

Intraoperative Analysis

Some embodiments include an intraoperative analysis performed byintraoperative module 300. The intraoperative analysis relies on thepelvic position data to calculate inclination and anteversion dataduring surgery. To do this, an embodiment of the intraoperative module300 performs the steps detailed in the flowchart in FIG. 21 .

The intraoperative analysis is initiated at step 602 eitherautomatically or in response to a user instructing intraoperative module300 to execute the intraoperative analysis. At step 604, imageacquisition module 302 acquires an intraoperative AP image of apatient's pelvic region while the patient is in a supine position on anOR table. In most cases, intraoperative images will be taken using afluoroscopic c-arm. However, the intraoperative images may be retrievedin any manner known to a person of ordinary skill in the art. Inaddition, the image may be loaded into the system through a direct cableconnection or any other communication method.

Some embodiments include an image orientation step to modify one or moreimages to better capture the patient's pelvic position/orientation as itexists in the OR. Alternatively, the image capturing device is firstproperly oriented prior to capturing the image to ensure that the imagedepicts the pelvis in the same position/orientation as it exists inreality. In some embodiments, the user is provided with the option tomanually rotate the intraoperative image as needed to better capture thetrue orientation of a patient's pelvis in reality. In some embodiments,the system will use pelvic position change data as input into theacetabular component positioning intraoperative module to account forpelvic position and/or c-arm position changes when calculatinganteversion and inclination.

Once the intraoperative AP image is acquired, image annotation module304 then digitally registers an anatomical landmark in the form of line160 across the neutral axis at step 606 (see FIG. 22 ). The neutral axis(aka the “trans-teardrop axis”) is a line extending between the inferiorpoints on both pelvic teardrops. In some embodiments, the neutral axisis a line extending to consistent points on the ischial tuberositystructures.

Similar to the preoperative analysis, the anatomical landmark used inthe intraoperative analysis may be points, lines, circles, or othertypes of digitally registerable annotations corresponding to one or moreaspects of the patient's anatomy. In some embodiments, the anatomicallandmarks are determined manually by a user. In some embodiments, imageannotation module 304 automatically identifies the anatomical landmarksthrough image recognition software or machine learning algorithms. Someembodiments employ a mix of automated and manual identification of theanatomical landmarks. Moreover, some embodiments, allow the user tomodify the location of the visually displayed anatomical landmarkspoints to account for imaging or location errors.

In some embodiments, some or all of the anatomical landmarks aredigitally inserted or overlaid onto the images to provide a visualindication of the location of the anatomical landmarks. While differentmethods of visually displaying the landmarks may be used, the term“digitally register” will be used herein to refer to any method used tovisually depict an anatomical landmark on a digital image. In someembodiments, intraoperative module 300 visually displays to a user eachinstance in which an anatomical landmark is digitally registered on oneof the intraoperative images similar to FIGS. 22-28 .

Referring back to FIG. 21 , at step 608, the user or system identifiesthe operative hip and annotation module 304 digitally registers pelvicteardrop brim line 162, which is illustrated in FIG. 23 . Pelvicteardrop brim line 162 extends between the pelvic teardrop on theoperative hip and runs across the pelvic brim. Because teardrop brimline 162 runs tangential to the pelvic brim there is no need for aspecific end point for the superior end of the line.

At step 610, the user and/or the system determines if the same vertebralanatomical landmark (the S1 endplate in the examples above) that wasused to calculate the SFP angle in the preoperative images isvisible/identifiable in the AP intraoperative image of the pelvis.Depending on the fluoroscopic c-arm used, it is possible that thevertebral anatomical landmark will not be clearly identifiable in theintraoperative pelvis image. If this happens, the system can skip steps612-618, and instead use the SFP angle from the preoperative AP supineimage and move to step 620. The preoperative SFP angle should be a closeapproximation to the intraoperative SFP angle. For best accuracy, thesurgeon should review the obturator foramen openings and confirm thatthey are consistent between the preoperative and intraoperative images.This will ensure that the SFP angle in the preoperative andintraoperative AP supine images are generally consistent.

If the vertebral anatomical landmark is clearly identifiable in theintraoperative pelvis image, at step 612, image annotation module 304positions digital line 164 across the vertebral anatomical landmarkconsistent with what was used in the preoperative analysis (see FIG. 24). Then at step 614, image annotation module 304 identifies center point166 of the contralateral femoral head using digitally registered circle168 as shown in FIG. 25 . At step 616, image annotation module 304digitally registers superior point 170 on the pubic symphysis.Calculation engine 306 can then determine the SFP angle based on firstline 176 extending between center 166 of the contralateral femoral headand midpoint 174 of the vertebral anatomical landmark line and secondline 172 extending between center 166 of the contralateral femoral headand superior point 170 on pubic symphysis. The angle between the twolines is the SFP angle. Calculation engine 306 determines the SFP angleat step 618 and pelvic position display module 308 displays the angle asshown in FIG. 26 .

In some embodiments, if the SFP angle in the intraoperative image variesby more than 5 degrees of the SFP angle calculated in the preoperativesupine image, a warning message will be displayed. This is a prompt toverify that the same vertebral anatomical landmark was used incalculating the SFP angle. If there is less than a 5-degree difference,the intraoperative module moves to step 620.

If the vertebral anatomical landmark is not clearly identifiable in theintraoperative pelvis image, the system provides an option toalternatively use the SFP angle calculated in the preoperative supineimage and move on to step 620. The preoperative SFP angle should be aclose approximation to the intraoperative SFP angle shown in the supineintraoperative image. The surgeon should visually confirm that thepelvis appears consistent by visual examination of the obturator foramenopenings in the preoperative and intraoperative radiographic images.

At step 620, image acquisition module 302 acquires an intraoperativeimage of the implanted acetabular cup component. In most cases,intraoperative images will be taken using a fluoroscopic c-arm. However,the intraoperative images may be retrieved in any manner known to aperson of ordinary skill in the art. In addition, the image may beloaded into the system through a direct cable connection or any othercommunication method.

At step 622, image annotation module 304 digitally registers teardropbrim line 162 on the intraoperative image of the implanted acetabularcup component, which is illustrated in FIG. 27 . Teardrop brim line 162runs tangential to the pelvic brim so there is no need for a specificend point for the superior end of the line. The software uses this lineto correlate the neutral axis on the intraoperative image of the pelvisto the image of the implanted acetabular cup component. Note that theuse of two images—with the acetabulum centered on the screen in one—isused to minimize any parallax effect.

At step, 624 the user manually, or image annotation module 304automatically, digitally registers tracking ellipse 164 over the rim ofthe acetabular cup component as shown in FIG. 28 . The intraoperativeplacement of digital tracking ellipse 164 assists in calculatinganteversion and inclination in the operative position as well as in theseated and standing positions based upon changes in pelvic tilt.

The ellipse is drawn so that the major axis of the ellipse representsthe inclination angle relative to the neutral axis. Thus,increasing/decreasing anteversion will appropriately increase/decreasethe size of the digital tracking ellipse's minor axis, consistent withthe calculation. Similarly, a user can increase/decrease the inclinationof the ellipse, which will appropriately increase/decrease the angle ofthe digital tracking ellipse's major axis, relative to the neutral axisand associated to the neutral axis in the image of the pelvis throughthe identification of the pelvic brim line in each image.

In other words, adjusting the inclination will rotate the ellipse andadjusting the anteversion will expand or contract the ellipse opening.In some embodiments, ellipse angle data can be displayed using eitherthe anatomic or radiographic mode. The anatomic mode is recommendedbecause it corrects for 3-d to 2-d image differences and for this reasonit provides a more accurate depiction of anteversion and inclination. Insome embodiments, the system displays the image of the pelvis in a small“picture in picture” window and depicts both the “pelvic brim” and“neutral axis” or “trans-teardrop” lines.

In some embodiments, the user can manually position the ellipse, using adigital handle, so that it overlays the opening of the acetabularcomponent in the radiographic image being analyzed. The user may resizeand reposition the ellipse as required. In some embodiments, the surgeoncan continue to re-position the acetabular cup component, and shootadditional images, until the ellipse and image indicate that they havematched their desired inclination and anteversion.

The image of (1) the pelvis and (2) the centered acetabular componentwill be rotated on screen so that the neutral axes are aligned along thex-axis of the screen. This will ensure that the inclination representedby the digital tracking ellipse will always appear consistently on thescreen, which is beneficial for users.

Once the tracking ellipse positioning is complete, the system can usethe location of the tracking ellipse to determine the intraoperativeanatomic inclination and anteversion of the acetabulum cup componentshown in the intraoperative image. It should be noted that other systemsand methods known to a person of ordinary skill in the art for trackingthe position and orientation of implanted objects can be used todetermine the position and orientation of the acetabular cup componentshown in the intraoperative image(s).

At step 626, calculation engine 306 uses preoperative pelvic positioning(“pelvic tilt”) data from output communication module 210 andintraoperative data to calculate anteversion and inclination data of theacetabular cup component for the relaxed seated, supine and standingpositions. These calculations incorporate the patient's unique SFPinformation to calculate the effect of pelvic position data from thepreoperative analysis that was previously performed.

More specifically, the system can determine the anteversion andinclination of the acetabular cup component in the seated, supine, andstanding anatomical positions through Equations 6-12 below. Equation 6establishes the intraoperative sacral slope based on the pelvicincidence, SFP constant, and measured intraoperative SFP angle.

SS_(I)=PI−(SFP_(constant)−SFP_(I))  (Eq. 6)

where SS_(I) is the intraoperative sacral slope, PI is the pelvicincidence (which remains constant for a patient in any anatomicalposition), SFP_(constant) is the constant that provides the relationshipbetween SFP and SPT angles as introduced in Eq. 1, and SFP_(I) is themeasured SFP angle in the intraoperative image. If the SFP angle in theintraoperative supine image cannot be accurately determined, the SFP_(I)in Eq. 6 is replaced with the preoperative SFP angle.

Equations 7-12 are then used to calculate the inclination andanteversion values when the patient is in the seated, supine, andstanding anatomical positions.

Inclination_(Seated)=Inclination_(m)+(SS_(PSeated)−SS_(I))*Inc_(Co)  (Eq.7)

Anteversion_(Seated)=Anteversion_(m)+(SS_(PSeated)−SS_(I))*Ant_(Co)  (Eq.8)

Inclination_(Supine)=Inclination_(m)+(SS_(PSupine)−SS_(I))*Inc_(Co)  (Eq.9)

Anteversion_(Supine)=Anteversion_(m)+(SS_(PSupine)−SS_(I))*Ant_(Co)  (Eq.10)

Inclination_(Standing)=Inclination_(m)+(SS_(PStanding)−SS_(I))*Inc_(Co)  (Eq.11)

Anteversion_(Standing)=Anteversion_(m)+(SS_(PStanding)−SS_(I))*Ant_(Co)  (Eq.12)

Where Ant_(Co) is an anteversion coefficient, Inc_(Co) is an inclinationcoefficient, Inclination_(m) is the measured inclination of theacetabular cup component in the intraoperative image, Anteversion_(m) isthe measured anteversion of the acetabular cup component in theintraoperative image, SS_(I) is the intraoperative sacral slope, andSS_(PSeated) is the preoperative sacral slope in the seated position,SS_(PSupine) is the preoperative sacral slope in the supine position,and SS_(PStanding) is the preoperative sacral slope in the standingposition.

In some embodiments, the anteversion coefficient is 0.75. In someembodiments the anteversion coefficient is a value within the range of0.7-0.8. In some embodiments it is a value within the range of 0.6-1. Insome embodiments, the inclination coefficient is 0.29. In someembodiments, the inclination coefficient is a value within the range of0.2-0.4.

At step 628, acetabular component display module 308 displays the imagesto the user and acetabular component position output module 310 presentsthe position data to the user on a graphic interface similar to FIG. 28. Based on the patient's intraoperative pelvic tilt and the inclinationand anteversion angles of the implanted cup component, the systemdisplays the dislocation risk of the prosthetic hip when the patient isseated, standing, and lying as depicted in an exemplary form on the leftside of the screen. Moreover, the inclination values and anteversionvalues are displayed and the end user is provided with the ability toadjust the anteversion and inclination values of the acetabular cupcomponent using the graphic interface buttons. The inclination andanteversion can be adjusted in both the positive and negativedirections. When the end user modifies the inclination and anteversionof the acetabular cup, the system recalculates the dislocation risk ineach position to determine if the acetabular cup component needs to bereadjusted.

Preferably the display includes both a quantitative measurement of theanteversion and inclination values for the various anatomic locationsand qualitative indicators (colors to identify a safe zone, a mediumdislocation risk zone, and a high dislocation risk zone) to convey therisk of dislocation when the patient is in various anatomical positions.If the values are green, the patient is in a safe zone. If the valuesare yellow, the patient is in a medium risk zone. And if the values arered, the patient is in a high-risk zone. Similar to FIGS. 20 , thedisplay may include a tilt bar that includes both a quantitativemeasurement and a qualitative assessment of the risk of dislocation whenthe patient is sitting, lying, and standing.

Hardware and Software Infrastructure Examples

The present invention may be embodied on various computing systemsand/or platforms that perform actions responsive to software-basedinstructions. The following provides an antecedent basis for theinformation technology that may be utilized to enable the invention.

The computer readable medium described in the claims below may be acomputer readable signal medium or a computer readable storage medium. Acomputer readable storage medium may be, for example, but not limitedto, an electronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thecomputer readable storage medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any non-transitory, tangiblemedium that can contain, or store a program for use by or in connectionwith an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wire-line, optical fiber cable, radio frequency, etc., or any suitablecombination of the foregoing. Computer program code for carrying outoperations for aspects of the present invention may be written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, C#, C++, Visual Basic or thelike and conventional procedural programming languages, such as the “C”programming language or similar programming languages.

Aspects of the present invention may be described with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general-purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The advantages set forth above, and those made apparent from theforegoing description, are efficiently attained. Since certain changesmay be made in the above construction without departing from the scopeof the invention, it is intended that all matters contained in theforegoing description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention that, as amatter of language, might be said to fall therebetween.

What is claimed is:
 1. A method for preoperatively determininginclination and anteversion for an acetabular cup component of a hipimplant in several anatomical positions to determine a risk of hipdislocation in the several anatomical positions, comprising: acquiring aplurality of preoperative images of a patient's pelvic region, theplurality of preoperative images including: an anteroposterior image ofthe patient's pelvic region in a first anatomical position; a lateralimage of the patient's pelvic region in the first anatomical position;an image of the patient's pelvic region when the patient is in a secondanatomical position; an image of the patient's pelvic region when thepatient is in a third anatomical position; wherein at least the firstand second anatomical positions are distinct from each other;determining a sacral femoral pubic angle from the anteroposterior imageof the patient's pelvic region in the first anatomical position;determining a spinal pelvic tilt angle from the lateral image of thepatient's pelvic region in the first anatomical position; determining apatient specific sacral femoral pubic constant based on theanteroposterior image of the patient's pelvic region in the firstanatomical position and the lateral image of the patient's pelvic regionin the first anatomical position; determining a spinal pelvic tilt anglefrom the image of the patient's pelvic region in the second anatomicalposition; determining a pelvic tilt angle from the image of thepatient's pelvic region in the third anatomical position; whereby thecalculated pelvic tilt angles in the first anatomical position, secondanatomical position, and third anatomical position allow a surgeon todetermine how the inclination and anteversion for the acetabular cupcomponent of the hip implant will vary in each of the first anatomicalposition, second anatomical position, and third anatomical position. 2.The method of claim 1, wherein the first anatomical position is astanding position, the second anatomical position is a supine position,and the third anatomical position is a seated position.
 3. The method ofclaim 2, further including: acquiring a predetermined supine anteversionvalue and a predetermined supine inclination value; calculating a seatedanteversion of the acetabular cup component based on the predeterminedsupine anteversion value and the pelvic tilt angle in the secondanatomical position, and the pelvic tilt angle in the third anatomicalposition; calculating a standing anteversion of the acetabular cupcomponent based on the predetermined supine anteversion value, thepelvic tilt angle in the second anatomical position, and the pelvic tiltangle in the first anatomical position; calculating a seated inclinationof the acetabular cup component based on the predetermined supineinclination value, the pelvic tilt angle in the second anatomicalposition, and the pelvic tilt angle in the third anatomical position;calculating a standing inclination of the acetabular cup component basedon the predetermined supine inclination value, the pelvic tilt angle inthe second anatomical position, and the pelvic tilt angle in the firstanatomical position; and displaying to a user the calculated standinginclination of the acetabular cup component, the calculated standinganteversion of the acetabular cup component, the calculated seatedinclination of the acetabular cup component, and the calculated seatedanteversion of the acetabular cup component.
 4. The method of claim 3,wherein: calculating the seated anteversion of the acetabular cupcomponent for the seated position is based on:Anteversion_(Seated)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Seated))*Ant_(Co)wherein Anteversion_(Supine) is the predetermined supine anteversionvalue, SPT_(Supine) is the supine pelvic tilt angle, SPT_(Seated) is theseated pelvic tilt angle, and Ant_(Co) is an anteversion coefficient;calculating the standing anteversion of the acetabular cup component forthe standing position is based on:Anteversion_(Standing)=Anteversion_(Supine)+(SPT_(Supine)−SPT_(Standing))*Ant_(Co)wherein Anteversion_(Supine) is the predetermined supine anteversionvalue, SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) isthe standing pelvic tilt angle, and Ant_(Co) is the anteversioncoefficient; calculating the seated inclination of the acetabular cupcomponent for the seated position is based on:Inclination_(Seated)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Seated))*Inc_(Co)wherein Inclination_(Supine) is the predetermined supine inclinationvalue, SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) isthe standing pelvic tilt angle, and Inc_(Co) is an inclinationcoefficient; calculating the standing inclination of the acetabular cupcomponent for the standing position is based on:Inclination_(Standing)=Inclination_(Supine)+(SPT_(Supine)−SPT_(Standing))*Inc_(Co)wherein Inclination_(Supine) is the predetermined supine inclinationvalue, SPT_(Supine) is the supine pelvic tilt angle, SPT_(Standing) isthe standing pelvic tilt angle, and Inc_(Co) is the inclinationcoefficient.
 5. The system of claim 4, wherein the anteversioncoefficient is between 0.7 and 0.8.
 6. The system of claim 4, whereinthe inclination coefficient is between 0.2 and 0.4.
 7. The system ofclaim 2, wherein the predetermined supine anteversion value is initiallyset to a value between 20 and 30 degrees.
 8. The system of claim 2,wherein the predetermined supine anteversion value is adjustable by auser.
 9. The system of claim 2, further including qualitativelyconveying if the calculated standing inclination of the acetabular cupcomponent, the calculated standing anteversion of the acetabular cupcomponent, the calculated seated inclination of the acetabular cupcomponent, and the calculated seated anteversion of the acetabular cupcomponent are each in a low risk, medium risk, or high-risk zone for hipdislocation.
 10. The method of claim 1, wherein determining the sacralfemoral pubic angle from any anteroposterior image of the patient'spelvic region includes: digitally registering a vertebral anatomicallandmark on the anteroposterior image; digitally registering the centerpoint of the femoral head on the anteroposterior image; digitallyregistering a position of a superior point on a pubic symphysis on theanteroposterior image; digitally registering a femoral pubic lineextending from the center point of the femoral head to the position ofthe superior point on the pubic symphysis on the anteroposterior image;and calculating the sacral femoral pubic angle, which corresponds to anangle between the femoral pubic line and a line extending from thecenter point of the femoral head to the vertebral anatomical landmark.11. The method of claim 1, wherein determining the spinal pelvic tiltangle from any lateral image includes directly determining the spinalpelvic tilt angle by: digitally registering a vertebral anatomicallandmark on the lateral image, wherein the vertebral anatomical landmarkis a midpoint on a line corresponding to a patient's sacral endplate;digitally registering a center point of a femoral head on the lateralimage; digitally registering a vertical axis on the lateral image thatis vertically aligned with the center point of the femoral head; andcalculating the spinal pelvic tilt angle, which corresponds to an anglebetween the vertical axis and a line extending from the center point ofthe femoral head to the vertebral anatomical landmark.
 12. The method ofclaim 1, wherein determining the spinal pelvic tilt angle from anylateral image includes indirectly determining the spinal pelvic tiltangle by: digitally registering a vertebral anatomical landmark on thelateral image, wherein the vertebral anatomical landmark is a linecorresponding to the patient's sacral endplate; digitally registering ahorizontal axis on the lateral image that is horizontally aligned with asuperior point on the line corresponding to the patient's sacralendplate; determining a sacral slope angle, which corresponds to anangle between the horizontal axis and the vertebral anatomical landmark;and calculating the spinal pelvic tilt angle by subtracting the sacralslope angle from a pelvic incidence of the patient.
 13. The system ofclaim 1, further including: acquiring an intraoperative image depictingan implanted acetabular cup component within a patient's body;determining an intraoperative inclination and an intraoperativeanteversion of the implanted acetabular cup component; and calculatingan intraoperative standing inclination of the acetabular cup componentan intraoperative standing anteversion of the acetabular cup component,an intraoperative seated inclination of the acetabular cup component,and an intraoperative seated anteversion of the acetabular cupcomponent.
 14. The method of claim 1, wherein: the image of thepatient's pelvic region when the patient is in the second anatomicalposition is an anteroposterior image; and determining the spinal pelvictilt angle of the patient's pelvis in the second anatomical positionincludes subtracting a sacral femoral pubic angle from theanteroposterior image of the patient's pelvic region in the secondanatomical position from the patient specific sacral femoral pubicconstant.
 15. A computer system having one or more computers performinga method for preoperatively determining inclination and anteversion foran acetabular cup component of a hip implant in several anatomicalpositions to determine a risk of hip dislocation in the severalanatomical positions, the method comprising: acquiring a plurality oftwo-dimensional preoperative images of a patient's pelvic region, theplurality of preoperative images including: an anteroposterior image ofthe patient's pelvic region in a first anatomical position; a lateralimage of the patient's pelvic region in the first anatomical position;an image of the patient's pelvic region when the patient is in a secondanatomical position; an image of the patient's pelvic region when thepatient is in a third anatomical position; wherein the first, second,and third anatomical positions are distinct from each other; determininga sacral femoral pubic angle from the anteroposterior image of thepatient's pelvic region in the first anatomical position; determining aspinal pelvic tilt angle from the lateral image of the patient's pelvicregion in the first anatomical position; determining a patient specificsacral femoral pubic constant by adding the sacral femoral pubic anglefrom the anteroposterior image of the patient's pelvic region in thefirst anatomical position to the spinal pelvic tilt angle from thelateral image of the patient's pelvic region in the first anatomicalposition; determining a spinal pelvic tilt angle from the image of thepatient's pelvic region in the second anatomical position; determining apelvic tilt angle from the image of the patient's pelvic region when thethird anatomical position; whereby the calculated pelvic tilt angles inthe first anatomical position, second anatomical position, and thirdanatomical position allow a surgeon to determine how the inclination andanteversion for the acetabular cup component of the hip implant willvary in each of the first anatomical position, second anatomicalposition, and third anatomical position.
 16. The system of claim 15,wherein the first anatomical position is a standing position, the secondanatomical position is a supine position, and the third anatomicalposition is a seated position.
 17. The system of claim 16, furtherincluding: acquiring a predetermined supine anteversion value and apredetermined supine inclination value; calculating a seated anteversionof the acetabular cup component based on the predetermined supineanteversion value and the pelvic tilt angle in the second anatomicalposition, and the pelvic tilt angle in the third anatomical position;calculating a standing anteversion of the acetabular cup component basedon the predetermined supine anteversion value, the pelvic tilt angle inthe second anatomical position, and the pelvic tilt angle in the firstanatomical position; calculating a seated inclination of the acetabularcup component based on the predetermined supine inclination value, thepelvic tilt angle in the second anatomical position, and the pelvic tiltangle in the third anatomical position; calculating a standinginclination of the acetabular cup component based on the predeterminedsupine inclination value, the pelvic tilt angle in the second anatomicalposition, and the pelvic tilt angle in the first anatomical position;and displaying to a user the calculated standing inclination of theacetabular cup component, the calculated standing anteversion of theacetabular cup component, the calculated seated inclination of theacetabular cup component, and the calculated seated anteversion of theacetabular cup component.
 18. The system of claim 15, whereindetermining the sacral femoral pubic angle from any anteroposteriorimage of the patient's pelvic region includes: digitally registering avertebral anatomical landmark on the anteroposterior image; digitallyregistering the center point of the femoral head on the anteroposteriorimage; digitally registering a position of a superior point on a pubicsymphysis on the anteroposterior image; digitally registering a femoralpubic line extending from the center point of the femoral head to theposition of the superior point on the pubic symphysis on theanteroposterior image; and calculating the sacral femoral pubic angle,which corresponds to an angle between the femoral pubic line and a lineextending from the center point of the femoral head to the vertebralanatomical landmark.
 19. The system of claim 15, wherein determining thespinal pelvic tilt angle from any lateral image includes directlydetermining the spinal pelvic tilt angle by: digitally registering avertebral anatomical landmark on the lateral image, wherein thevertebral anatomical landmark is a midpoint on a line corresponding to apatient's sacral endplate; digitally registering a center point of afemoral head on the lateral image; digitally registering a vertical axison the lateral image that is vertically aligned with the center point ofthe femoral head; and calculating the spinal pelvic tilt angle, whichcorresponds to an angle between the vertical axis and a line extendingfrom the center point of the femoral head to the vertebral anatomicallandmark.
 20. The system of claim 15, wherein determining the spinalpelvic tilt angle from any lateral image includes indirectly determiningthe spinal pelvic tilt angle by: digitally registering a vertebralanatomical landmark on the lateral image, wherein the vertebralanatomical landmark is a line corresponding to the patient's sacralendplate; digitally registering a horizontal axis on the lateral imagethat is horizontally aligned with a superior point on the linecorresponding to the patient's sacral endplate; determining a sacralslope angle, which corresponds to an angle between the horizontal axisand the vertebral anatomical landmark; and calculating the spinal pelvictilt angle by subtracting the sacral slope angle from a pelvic incidenceof the patient.